1. Field of the Invention
The present invention relates to a shock absorber for a vehicle, and more particularly, to a monotube-type shock absorber for a vehicle which can adjust a height of the vehicle.
2. Description of Related Art
A shock absorber configuring a suspension of a vehicle is an apparatus installed between an axle and a body of the vehicle to absorb vibrations and impacts received by the axle from a road surface while the vehicle is driven and improve riding quality, and serves to provide driving stability and comfortable ride.
Manual shock absorbers widely used conventionally have been developed with only improvement of riding quality and adjustment stability being focused, and accordingly, it is impossible to stably control vehicle postures varying during a travel of the vehicle.
In order to supplement this shortcoming, vehicle height controlled shock absorbers have been developed, and the vehicle height controlled shock absorbers generate damping forces by using hydraulic pressures. Further, the vehicle height controlled shock absorbers additionally function to not only absorb vibrations to improve riding quality and adjustment stability and but also always maintain a height of a vehicle varying during a travel of the vehicle constantly and stably.
FIG. 1 illustrates a shock absorber according to the related art which can adjust a height of a vehicle, and the shock absorber includes a twin tube-type cylinder 1 having an inner tube 1a and an outer tube 1b, a piston 2 installed within the inner tube 1a to reciprocally move along a lengthwise direction of the inner tube 1a, a piston rod one end of which is connected to the piston 2 and an opposite end of which passes through the cylinder 1, an oil pump 4 for generating a hydraulic pressure, and a reserve tank 5 for storing an oil.
Further, a spring valve 6 for connecting the outer tube 1b and the inner tube 1a is installed on a bottom surface of the inner tube 1a, a damping force valve 7 is installed in the piston 2, an leveling valve 9 is installed at an end of an oil passage 8 connecting the inner tube 1a and the reserve tank 5. In addition, a valve hole (not shown) through which an oil can flow is formed in the leveling valve 9, and a piston hole 2a connecting the inner 1a and an interior space of the piston 3 is formed in the piston 2.
An oil is filled in a space between the inner tube 1a and the outer tube 1b, an inner space of the inner tube 1a, and an inner space of the piston rod 2.
The state of FIG. 1A is an initial state where neither a bump nor a rebound situation occurs, in which state the spring valve 6 is opened and the leveling valve 9 is closed. Then, the oil in the inner tube 1a absorbs impacts and vibrations while smoothly flowing through the piston hole 2a, and valve holes formed in the spring valve 6, the damping force valve 7, and the leveling valve 9.
The state of FIG. 1B is a state where a height of the vehicle is raised, in which state, accordingly, the oil in the reserve tank 5 is introduced into interior spaces of the inner tube 1a and the piston rod 3 through an operation of the oil pump 4. Then, the spring valve 6 is closed and the leveling valve 9 is opened, so that the above-described height raised state is maintained by the rebound side shock absorber during a straight travel of the vehicle and by the outer turn wheel side shock absorber during a turn of the vehicle
The state of FIG. 1C is a state where a height of the vehicle is lowered, in which state the oil in the inner tube 1a is withdrawn into the reserve tank 5 and accordingly, the piston 2 is lowered. Then, the spring valve 6 is opened and the leveling valve 9 is closed, in which case the bump side shock absorber and the inner turn wheel side shock absorber maintains a state where a height of the vehicle is lowered during a straight travel of the vehicle.
However, the shock absorber according to the related art is a twin tube-type shock absorber including a cylinder 1 having an inner tube 1a and an outer tube 1b, but the twin tube-type shock absorber needs to be small-sized. In particular, since a sufficient installing space needs to be secured, the twin tube-type shock absorber is disadvantageous in the layout of the vehicle.
In addition, according to the twin tube-type shock absorber according to the related art, a separate valve (spring valve) needs to be installed to interrupt a passage between the inner tube 1a and the outer tube 1b, which makes the structure of the shock absorber complex and increases manufacturing costs.
The items described as the related art are just to help understanding of the background of the present invention, and shall not be construed to admit that they belong to the related art well known to those skilled in the art to which the present invention pertains.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.